The present invention relates to a foldable carrier such as a stretcher comprising on the one hand a thin first layer of an all-round flexible material of large wear and tear strength, having a substantially elongate basic form and forming a carrier, for instance for enabling the use of the carrier as a stretcher, and on the other hand a considerably thicker second layer of elongate basic form which is permanently joined or integrated with the carrier layer and which consists of a porous or fluffy soft material being intended for forming a stretcher part for enabling a comfortable reclining upon the underlay.
According to the stretcher of the present invention, two layers are, preferably, intimately integrated with another being formed of one and the same polymer material, for instance polyethylene, the thin carrier layer having a thickness of about 0.6 to 1 mm and a density of 0.9 to 1.0 kg/dm.sup.3, while the thick, porous layer has a thickness of about 5 mm and a density which is many times lower, for instance about 0.05 kg/dm.sup.3. Thus, according to its preferred embodiment, the stretcher has a total thickness of around 6 mm; this making it possible to roll it into a spirally wound roll which can be stored in an easy way, e.g. on or in a rucksack. A substantial advantage is that, when needed, it may be quickly and smoothly used as a stretcher. Of this reason, this product is particularly well suited for being stretcher may advantageously be included into the pack of a soldier and fulfil a double function for serving not only as a heart insulating and a point load equalizing sleeping underlay on the top of a bed of brushwood or similar, but also as a flexible stretcher construction in the case when the soldier or persons in his proximity would be injured. However, a shortcoming of this stretcher is that its limited thickness (6 mm in the preferred embodiment) gives a very mediocre, if not to say a directly bad shock absorbing and load distributing capacity. Thus, if the underlay is laid directly upon a hard, plane surface, e.g., upon a stiff bottom of a bed, the comparatively thin, porous layer does not offer any reposing comfort whatsoever.
Another general shortcoming of the prior art technology is the fact that stretchers rarely or never are accessible in a satisfactorily large number at or in the proximity of general establishments of different sorts. For instance, in railway and underground train sets often only one, or possibly a few stretchers (in worst case, none at all) are in readiness, which, what is more, not seldom are stowed away in difficultly accessible spaces, occasionally forgotten by the responsible staff. If an accident with many injuries on humans occurs, then the absence of sufficiently many easily accessible stretchers constitutes a circumstance which makes the required rescue work more difficult and retards it, sometimes to such an extent that the injuries are seriously aggravated and even become fatal.
The present invention aims at further developing the underlay unit known from WO87/04614 in such a way that, besides being usable as a stretcher, it also may be used as a comfortable stretcher directly upon a plane, hard surface. Thus, a primary object of the invention is to create an underlay unit which in a state of readiness, in which it is ready to be quickly used as a stretcher, may be used in a general way as a shock absorbing and/or load distributing soft unit, e.g., as an effect or part of an effect. In other words, during a long time in a storage or readiness state the unit shall be usable as a shock absorbing and/or supporting soft part, e.g. in the shape of a support-forming part of the back or a seat-forming part, whereafter it shall be possible to quickly and easily convert it into a stretcher.
Different forms of flexible mattresses for rescuing and patient evacuating proposes are previously disclosed in WO-A-91/18576, U.S. Pat. No. 4,124,908, U.S. Pat. No. 4,186,453 and U.S. Pat. No. 4,442,557. However, these mattresses lack the slits in the mattresses which are characteristic for the present invention and which form longitudinal folding lines in order to make possible a folding of the mattresses into a package.
Further, in WO-A-86/02814 a mattress-like bed underlay is disclosed which is capable of being folded into a seat-forming package. However, in this case, the folding takes place laterally, the bed underlay lacking any sort of longitudinal slits of the sort that characterizes the invention. Nor is the underlay shown in this document capable of being used as a stretcher. Furthermore, the Norwegian design registration No. 68206 provides the mattress with lateral folding notches.